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  • 1
    Digitale Medien
    Digitale Medien
    Transcription-Independent Activation of Ornithine Decarboxylase Activity by Heparin in Cloned Cerebral Endothelial Cells (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 60 (1993), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: Heparin, a highly sulfated glycosaminoglycan, is known to be obligatory for long-term endothelial cell cultures; it potentiates the mitogenic activities of endothelial cell growth factors and prolongs the replicative life span of the cells. Here we have shown that besides its growth factor-supportive role, heparin exerts a specific action on cerebral capillary endothelial cells (cECs), unrelated to serum or growth factors, by increasing activity of ornithine decarboxylase (ODC; EC 4.1.1.17) in these cells. For our experiments we have used two different types of cloned cECs: type I cECs, grown in the presence of endothelial cell growth factor and heparin, and type II cECs, usually cultivated without growth factors. Heparin action on ODC activity was shown to be dose dependent within the range of 1–100 μg/ml. Increasing concentrations of or depletion of endothelial cell growth factor from type I cultures had no effect on ODC activity. The increase in enzyme activity was highest after 30 min to 1 h of heparin treatment. As evidenced by northern analysis, the heparin-mediated enhancement of ODC activity was not accompanied by changes of ODC mRNA levels. Studies of DNA replication revealed that in the absence of heparin-binding growth factors, heparin did not affect the proliferative activity of cloned cECs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1993.tb03316.x
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  • 2
    Digitale Medien
    Digitale Medien
    Penetration and equilibration of injected electrons into a high-current hydrogen pseudospark-type plasma (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 512-516 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The penetration and equilibration of the velocity distribution function of an initially monoenergetic electron beam with energies of 50, 100, and 500 eV which is injected into a Maxwellian "bulk'' hydrogen pseudospark or back-lighted thyratron plasma ( j≈104 A/cm2, Te≈1 eV, ne=1–3×1015 cm−3) is evaluated using a Fokker–Planck equation. The electron beam considered here is the part that is produced during the conductive phase by the electric field in the cathode fall. The beam is estimated to traverse the electrode gap without equilibration with the background plasma if the plasma density is ≤2.5×1015 cm−3.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.346821
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  • 3
    Digitale Medien
    Digitale Medien
    Homogeneous cylindrical plasma source for short-wavelength laser experiments (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2619-2621 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A plasma source suitable for repetitive operation, going beyond single shot experiments for research into soft x-ray lasers, is reported. Successful operation of an ultrafast, small-diameter, highly uniform z pinch has been achieved at currents of 35–50 kA, for a variety of gases and a large range of mass densities. Due to an efficient preionization of the working gas, a high-temperature and a high cooling rate of the plasma column are obtained. The plasma is less than 1 mm in radius, over 30 mm long, and over 1018 cm−3 ion density. A soft x-ray recombination laser experiment for the λ≈182 A(ring) Balmer-alpha-like transition in C vi is proposed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.104812
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  • 4
    Digitale Medien
    Digitale Medien
    High current plasma based electron source (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 434-436 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: This letter analyzes the transport of an electron beam that is produced during the conductive phase operation in the cathode fall of a pseudospark or back lighted thyratron for applications that require a high brightness electron source. The beam is estimated to traverse the device without thermalization if the plasma density is ≤2.5×1015 cm−3. High brightness electron sources are necessary for various new plasma based devices, and these results encourage consideration of this electron beam as a new candidate for applications including microwave generation sources, electron sources for accelerators, and plasma based accelerators which require improved cathodes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.103657
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  • 5
    Digitale Medien
    Digitale Medien
    Enzymes of Androgen Formation and Degradation in the Human Prostate (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 595 (1990), S. 0 
    Details
    ISSN: 1749-6632
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Allgemeine Naturwissenschaft
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1749-6632.1990.tb34282.x
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  • 6
    Digitale Medien
    Digitale Medien
    Phenology and photosynthetic activity in sterile and fertile sporophytes of Dryopteris filix-mas (L.) Schott (1991)
    Springer
    Oecologia 86 (1991), S. 159-162 
    Details
    ISSN: 1432-1939
    Schlagwort(e): Dryopteris filix-mas ; Fertile and sterile life phases ; Overwintering ; Phenology ; Photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary This study describes the phenology of sporophytes of the fern Dryopteris filix-mas in relation to whole plant development. Sterile and fertile potted sporophytes were set out at an exposed site and the seasonal development of the fronds was measured from the commencement of unfolding, through the phase of increasing length, up to discoloration. The physiological activity of the fronds was determined by measuring photosynthetic gas exchange. The fronds of sterile sporophytes unfolded in April, about a week earlier than those of fertile plants, but the colour had already begun to turn in September and their life span was 1–2 months shorter. However, between mid-June and the end of August the sterile sporophytes put out several sets of new fronds: these overwintered without changing color and were still photosynthetically active in the following spring. All types of fronds were fully expanded 1–2 months from the beginning of unfolding and, with a natural supply of CO2, had similar maximum net photosynthetic rates of 8–9 μmol/m2 · s. The decline in photosynthetic performance began before symptoms of senescence were visible and was due to decreased efficiency of the mesophyll. It is concluded that the phenology of D. filix-mas changes with transition from the sterile to the fertile phase. Whereas fertile sporophytes are genuinely summergreen, the sterile sporophytes with their summer fronds remain green throughout the winter and should therefore be termed semi-evergreen. The formation of overwintering summer shoots clearly extends the period of photosynthetic productivity of sterile sporophytes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00317526
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  • 7
    Digitale Medien
    Digitale Medien
    Formation of field discontinuities and islands in visual cortical maps (1994)
    Springer
    Biological cybernetics 70 (1994), S. 525-531 
    Details
    ISSN: 1432-0770
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Informatik , Physik
    Notizen: Abstract The representations of visual hemifields in the extrastriate areas of various species exhibit field discontinuities and islands. We propose that these violations of retinotopy are a developmental consequence of the elongated shape of the respective cortical areas. To substantiate this claim, we investigated a model of activity-driven map formation. In agreement with observations, this model yields maps with field discontinuities if the cortical areas exceed a threshold elongation. Moreover, within the same model island representations in the periphery and the area centralis can also be understood. A multistability of the solutions in the model gives a very simple explanation for the observed interindividual variability of maps in cats. The model leads to a prediction of the radial dependence of the areal magnification factor near field discontinuities, which could be accessible for a high precision mapping experiment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00198805
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  • 8
    Digitale Medien
    Digitale Medien
    Effects of thiopentone/suxamethonium on intraocular pressure after pretreatment with alfentanil (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 311-313 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Intraocular pressure, Alfentanil pretreatment ; suxamethonium, thiopentone
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The effects of pretreatment with alfentanil on intraocular pressure (IOP) were investigated in 40 patients undergoing ophthalmic surgery. Patients were randomly allocated to two study groups. Group 1 patients (n=20) received alfentanil 15 μg · kg−1, vecuronium 0.01 mg · kg−1, thiopentone 3-4 mg · kg−1, and suxamethonium 1 mg · kg−1 for anaesthetic induction, whereas patients in group 2 (n = 20) received vecuronium 0.01 mg · kg−1, thiopentone 3–4 mg · kg−1, and suxamethonium 1 mg · kg−1. A total of seven measurements of intraocular pressure were taken in each patient, starting before premedication and ending after extubation of the trachea. In group 2 patients, there was an increase in IOP after endotracheal incubation. In group 1 patients, a decrease in IOP occurred which was related to the decrease in arterial blood pressure. We conclude that alfentanil pretreatment can prevent the increase in IOP following suxamethonium administration.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02333030
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  • 9
    Digitale Medien
    Digitale Medien
    Formation of field discontinuities and islands in visual cortical maps (1994)
    Springer
    Biological cybernetics 70 (1994), S. 525-531 
    Details
    ISSN: 1432-0770
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Informatik , Physik
    Notizen: Abstract. The representations of visual hemifields in the extrastriate areas of various species exhibit field discontinuities and islands. We propose that these violations of retinotopy are a developmental consequence of the elongated shape of the respective cortical areas. To substantiate this claim, we investigated a model of activity-driven map formation. In agreement with observations, this model yields maps with field discontinuities if the cortical areas exceed a threshold elongation. Moreove r, within the same model island representations in the periphery and the area centralis can also be understood. A multistability of the solutions in the model gives a very simple explanation for the observed interindividual variability of maps in cats. The model leads to a prediction of the radial dependence of the areal magnification factor near field discontinuities, which could be accessible for a high precision mapping experiment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004220050055
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  • 10
    Digitale Medien
    Digitale Medien
    Schriftenschau (1991)
    Springer
    Journal of ornithology 132 (1991), S. 224-235 
    Details
    ISSN: 1439-0361
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01647282
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